[in Japanese]

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 This paper presents a snow-fall, load and melt model based on snow depth, precipitation, and meteorological data from the Hokuriku region of Japan, which is known worldwide as a heavy snow region. The model includes sub-models for the determination of snow-fall and snow melting, and for calculation of the densities of fresh snow and the snow layer. Daily snow depth was calculated in comparison to observed depths. Air temperature and humidity data were selected as factors related to snow-fall. In the snow loading sub-model, fresh snow density and average density of the snow layer were calculated separately. Snow melt was caluculated using a simple equatuion incorporating air temperature, net radiation, and soil heat flux. Calculated results showed good agreement with observed snow depth data and obseved snow density. Assessment of the importance of model parameters and factors revealed that some had negligible effects on practical calculations.

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 To evaluate the effects of the forest floor status on surface runoff generation occurring on forested slopes, we measured the forest floor cover percentage, surface runoff, and soil moisture contents of each bounded 1.0 m² plot on hillslopes in a Japanese cypress (Chamaecyparis obtusa) plantation (CY) and a nearby deciduous broad-leaved forest composed mainly of Konara oak (Quercus serrata) (KO) in Gunma Prefecture, Japan. The CY forest floor was partially covered by litter, with no understory vegetation. In contrast, the KO forest floor was covered almost completely with either litter or understory vegetation during observation periods. Surface runoff was generated for most rainfall events in both plots, but the saturated hydraulic conductivity in the soil profile was much higher than the observed rainfall intensity. The water drop penetration time, used as an index of water repellency in surface soils, was far longer for CY than for KO. Surface runoff coefficients, which are calculated as ratio of surface runoff to throughfall for a rainfall event, were negatively correlated with the initial soil water content before rainfall events in CY. These results show that the stronger repellency under drier conditions of surface soils in CY contributed to greater surface runoff generation. In contrast, variation in the surface runoff coefficients in KO was less than that in CY. Surface runoff generation was observed under conditions of lower rainfall intensity. These results suggest that the water flow associated with the litter layer (litter flow) was generated in KO.

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 The urban energy balance (UEB) is useful for elucidating unique urban climate phenomena such as localized heavy rains and the urban heat island effect. The Comprehensive Outdoor Scale Model Experiment for Urban Climate(COSMO) was conducted to investigate urbanization effects (i.e., surface geometry changes) on UEB. COSMO incorporates idealized miniature cities with no vegetation, no human activity, and no heterogeneity of the surface geometry. This study provides a review and examination of UEB obtained from COSMO and field observations.Urbanization enhances daytime heat storage and nighttime sensible heat flux, thereby increasing the thermal inertia of the system. The reasons for such changes using COSMO data are explained. Furthermore, variation of UEB among cities and seasons is presented. Its causes are explained. Additionally, UEB modelling is presented along with a case of COSMO data application in parameterization of roughness length for heat, a key aerodynamic land surface parameter for UEB modelling.

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 An Open Forum “Toward Great Progress of HRL (Hydrological Research Letters) by Inter-academic-society Collaboration” was held on 9^th September 2015 at Minami-Osawa Campus, Tokyo Metropolitan University. Keynote speeches were given by Makoto Taniguchi and Toshiyuki Nakaegawa, and then participants discussed on advantages/disadvantages of joint publication, current and future management of organizing committee, and what we need toward further progress of HRL.

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[in Japanese]

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[in Japanese]

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